Cathode structure



Dec. 6, 1932. ROMH1LD 1,890,339

CATHODE STRUCTURE Filed May 5, 1932 Inventor Edgar Rrnhild,

His Attorneg.

Patented. Dec. 6, 1932 "T UN E iFST T-ES ,nneeit n'oirmnn; on nE RLIN srnGLI'rz, E MANY, gamma 150 GENERAL I ELECTRIC COMPANY, A CORPORATIONDIE NEW gozax cannons sriwc'wnn Application filed May 3,1932, Serial No.

QThe present invention relates'to cathode structures, more especially to; those of -the directly-heated type designed-for large units. E

Cathodes composed of strips of metal for; example, nickel-chromium alloy, platinumiridium alloy, tungsten, molybdenum, etc, are frequently employed to obtain a large electron-emittingsurface in a simple cnstructional form. One disadvantage of such 10 strips, as employed by the prior art, is the relatively low resistance of the cathode as a whole, hence high current consumption,

which can be avoided only by the use of very thin strips, i. e., strips of relatively small "cross-section. However, when cathodes of the thin strip form are heated, their strength may be so reduced thatthe force exerted on them by the electrostatic field within the tube tends to bend and distort them out of 1 shape, particularly during the inverse voltage cycle when applied to arectifier. The cathodes may also be deformed by the magnetic field of the heating current which atfects them most deleteriously when the heating circuit is first closed. 7

An object of the present invention isto provide a strip form of cathode which is mechanically strong and resists the tendency to be pulled out of shape during operation. This object is attained in accordance with the present invention by securing together in any suitable manner, several metal strips of different lengths andcross-sections so as to form a rigid lattice work or grid structure.

Several exemplary embodiments are shown in the drawing in which Fig. 1 is a plan. view in perspective of an improved cathode structure, while Fig. 2 shows an end view of the structure. Fig. 3 is an end view of a modiv fied arrangement and Figs. 4 and 5 are diagrammatic plan views of several; typical forms which the cathode may take. Referring to Figs. 1 and 2, numerals 1 and 2 designate a pair of relatively thin metal strips ibent into a series of short, sharp turns or angles and having a configuration which as: a whole may be considered a zig-zag shape. The turns may be of equal or unequal length and when fitted together, preferably has a Q9 symmetrical design about the center line or well-known-manner. r If it is desired to design, a cathodeof the,

608,987, and m eeriiiany myfiei, 1931'. plane of contact. i There are twometalstrips 3 and t of smaller cross-section than the mam strips positioned between the latter where theygare 1 fitted together, at the upper and,

lower edges of the main strips and spanning;

the point-s'of-contact. The strips 1,2, 3, and 4 are rigidlysecuredxtogether in any suitable. manner,ffor example, by welding or riyeting; The endsofthest-rips land2, are drawn out.

to form yfiat reetilinear surfaces which con-" venientlyfmay serve as terminals for attachmentto leading-in conductors. J

vThe'narrow strips 3and 4 are employed] 7 chiefly for the purpose of enhancing the ri= gidity-ofthe structure. The resistanceof 6 E these-strips shouldbe predetermined bysuit v able "choice of material and cross-section so. e i s ps r chpp oxim te y he s e temperature, i. e., no higher temperature than; the ,main strips 1, a 2; Instead of employing 7 a pair of narrow stripssecuredto the-upper and loweredgs of the main strips,- one strip 5, positio ned at the center, asshown' in Fig. 3, may 'sometimesbe usedto advantage.

From the foregoing, it'is evident that the- 5 design and, construction of the improved cathodeis such as to afliord considerable rig gidity in alldirections notwithstanding thelargesurface offered and the small cross-sec? tio'nlof conductor, also the smallcurrent, re-. 9: quired; If desired, the cathodemay be coated with anelectrOn-emitting.substance-such as alkaline earth oxide in any suitable and f type described that will occupyarelat ively small space, the improved structure maybe bent into circular form, as shown in Figs. 4 and '5, without loss-of mechanical strength Fig. 4 shows'the cathode as conforming to-an incomplete circle with the terminals 6 posi tioned-relatively close together. .In Figtfi, the circle design iscomplete'and current may V be supplied to .the cathode through twoter- I minals 7, diametrically positioned on a pair of strips 8 which cross the oppositecorners of the main strips normalto the cornersispanned by the narrow stripsS 4. It is apparent that instead'of employing onlytwo. terminals, ad-

ditional 1terminals maybe located on cross 00 strips equidistantly spaced about the cathode so that the structure is readily adapted to a three? or more-phase current supply, employ- 'ing any standard form of connection.-

What I claim as new and desire to secure by V 1 Letters Patent oftheUnited States,"is-:

1. A"'cathodefo'r an electric discharge de 7 Vice comprising a plurality of 'main metal 7 strips bent into recurrent angular portions, said strips being substantiallyin abuttingjre-ge lation at the ends of each'strip and at inter'-" mediate portions, an auxiliarystripof metal a secured to the main strips at the places of contact therebetween wherebyallofthe strips are is rendered rigid.- p 7 Q; 'Acathode for an-"el'ectric dischargedevice comprising a pluralityof main metal secured together andthe structure as a whole r strips bent j into recurrentangular fportions, 1

. sai'd' strips being substantially inabu-tting re-' lat'ion 5 at the ends; of each-strip andat :intermediate portions, a plurality of auxiliary stripssecuredito' the edges of the'mainstrips 1 at the places of contact therebetween, where' byall of the stripsare secured together and the"structure as a -whole' is rendered rigid.

p 8. A'cathode ffonan electric discharge device comprising a plurality of'main metal stripsbent into'recurrent angular portions,

. said stripsbeingsubetantially in abutting re-flation at the ends of each strip and at inter-i unit is minimized. 7 g V I 6 A cathode for an electric discharge device comprising a'plurality of main'metal strips bent into recurrent angular portions,

said strips being substantiallyin abutting re-' lation'at the' endsi'of each strip and 'at. intermediate portions, an auxiliary strip of metal secured to the'main strips at the places of contact therebetween whereby all of' the strips are rigidly secu red-together, the relative re-.

lar form whereby the space occupied by the sistances of therespectivestrips being such 7 V thafithe'currents in the strips produce, ape

proXimat-elg equal heating eflects, said cathode being nt at the places ofcontact between the strips to a circular form whereby the space occupiedby thecathode is minimized,rand terminals for the.;cathodeflo'catedP: 7

at opposite diametral points;

In witness whereofl I havehereunto setimy hand. A 1

- EDGAR RoM I n-Y mediate portionsja pluralityOfMauXiIiary strips securedto theed es-of the main strips] at the places ofc ont'act tjerebetween, wh ereby-V all of the strips are rigidly secured together,

said auxiliary strips having a smaller cross- 7 c section than-the main strips whereby to: pre' clude the attainment during operation of a .temperaturehigher'than that of the main mediate portions, an auxiliary strip of metal secured'to the main strips at the places'of con tact therebetween whereby all of-the "strips form a rigid unit, all-of said stripsbeinggde signed as't'o cross-section and material to pass respective currents which produce appro'xi Y matfely equal heating effects.

5i A'cathode for anelectric discharge device comprising a plurality ofmain metal stripsbent into recurrent angular portions,

said strips being substantiallyin abutting reg l'ati'on at the ends of each strip and at'inte'rlmediate portions, an auxiliary strip of metal i v d secured to'the'main strips at the places ofcontact therebetweenwhereby all of the strips forma rigid unit, saidstrips ha'vingrelative resistances which preclude the auxiliary strip V reaching ahigheroperating temperature than a I r .t'hem'ain strips, said cathode being bent at the 5 places of contact between the"strips"toa'circu 

